Hundreds of years ago, in English, "boisterous" meant "rough, strong, active, and violent." We'd talk about boisterous winds that would sink your ship, or boisterous enemies that would attack you.
But these days, "boisterous" has a slightly nicer meaning. If you're being boisterous, you're being loud, lively, and playful. You're making lots of noise, you're playing pretty rough, and you're having a great time.
You might have boisterous friends, listen to boisterous music, go to boisterous parties, or play a boisterous game of football. And you might enjoy laughing boisterously: laughing in loud, wild, crazy-fun way.